Oh, she's not a Nazi, she was just a German in Nazi-ruled Germany who was kidnapped by Nazi scientists, for Nazi experimentation, and then brainwashed (by nazis) to serve the interests of the Reichstag.

Hey, you remember when he took money to guard Dr. Light, a known rapist, from the Justice League? Or that time he killed all his daughter's friends just to make her angry! His daughter hates him for being... a professional asshole who kills people for money. Truly a noble figure. A tragic backstory doesn't make a character noble. And Deathstroke deserves each of those tragedies. 

And for god's sake, the fact she's a Nazi isn't offensive or a big deal. Nazis in comics are a proud tradition, just look at Red Skull and Spy Smasher. The problem I have is that you're playing the cliche of Nazi superscience straight instead of having Dr. Von Murderschmidt experimenting on her to try to create the Ubermensch so he can get more Nazi Gold and brag about it at the office party.